Case burning rocket

ABSTRACT

A case-burning rocket booster includes a combustible case containing a solid rocket fuel, a combustion chamber adjustably coupled to the case for burning the case and the solid rocket fuel, a nozzle connected to the combustion chamber for expelling the burned case and fuel to generate thrust, and a drive system for pulling the combustion chamber and nozzle up the case as the case and fuel burn. A hybrid version of the case-burning rocket also includes an oxidizer supply system for supplying varying amounts of oxidizer to the combustion chamber to vary the thrust generated by burning the case and the fuel.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a Continuation-In-Part application which claimsbenefit of U.S. patent application Ser. No. 10/037,365 filed Jan. 4,2002, now U.S. Pat. No. 6,782,693, entitled “Case Burning Rocket” whichis hereby incorporated by reference, and benefit of co-pending,divisional U.S. patent application Ser. No. 10/910,400 to filed Aug. 3,2004 entitled “Method of Making a Threaded Rod for a Case BurningRocket” which is also hereby incorporated by reference.

BACKGROUND OF THE INVENTION

The present invention relates generally to solid rocket boosters. Moreparticularly, this invention pertains to a case-burning solid rocketbooster.

Core-burning solid rocket boosters are known in the art and aretypically fast burning systems that produce large amounts of thrust.These systems burn solid rocket fuel from the inside of the solid rocketfuel core outward to the pressure containing case enclosing the core.This type of burn pattern is designed to minimize exposure of the caseto the intense heat of combustion.

While this type of burn pattern produces high thrust, it also producesshort burn times and, as a result, core-burning solid rocket boostersrequire multiple stages to reach orbit or to propel long-range missilesystems. Examples of typical multiple-stage solid rocket boosters aredescribed in U.S. Pat. No. 5,070,691, issued to Smith et al. on Dec. 10,1991 and entitled “Solid Propellant Canister Loaded Multiple Pulsed orStaged Rocket,” and U.S. Pat. No. 4,956,971, issued to Smith on Sep. 18,1990 and entitled “Solid Propellant Canister Loaded Multiple Pulsed OrStaged Rocket Motor.” Multiple-stage solid rocket boosters, however, aremore complex than single-stage solid rocket boosters and are undesirablein some applications for this reason.

Core-burning solid rocket boosters also usually include a layer ofinsulation on the interior of the case in order to further protect thecase from the heat of combustion. In some applications, however, thislayer of insulation is undesirable because it adds weight and decreasesoverall rocket performance.

What is needed, then, is a solid rocket booster system that reduces toone stage or minimizes the number of stages required to reach orbit orto propel a long-range missile system and that does not require a layerof insulation to protect the case containing the solid rocket fuel fromthe heat of combustion.

SUMMARY OF THE INVENTION

Accordingly, one object of the present invention is to provide a solidrocket booster that requires fewer stages to reach orbit or to propel along-range missile system.

Another object of the present invention is to provide a solid rocketbooster that does not require a layer of insulation to protect the casecontaining the solid rocket fuel.

These objects, and other objects that will become apparent to someonepracticing the present invention, are satisfied by a case-burning solidrocket booster that includes a case containing a solid rocket fuel, acombustion chamber connected to the case for burning the case and thesolid rocket fuel, a nozzle connected to the combustion chamber forexpelling the burned case and fuel to generate thrust, and a drivesystem for pulling the combustion chamber and nozzle up the case as thecase and fuel burn. In an alternative embodiment, a hybrid version ofthe case-burning rocket includes an oxidizer supply system for supplyingvarying amounts of oxidizer to the combustion chamber to vary the thrustgenerated by burning the case and the fuel. In either embodiment, thebooster of the present invention burns the case as well as the solidrocket fuel and thereby increases the amount of thrust produced by thebooster. As a result, fewer stages are required to reach orbit or topropel a long-range missile system. In addition, no layer of insulationis required to protect the case containing the solid rocket fuel for thebooster of the present invention because the case is actually consumedduring the combustion process thereby increasing overall rocketperformance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of one embodiment of the present inventionof a case-burning rocket booster.

FIG. 2 is a cross-sectional view of the embodiment shown in FIG. 1.

FIG. 3 is an enlarged cross-sectional view of the combustion chamberseal assembly of the embodiment shown in FIGS. 1 and 2.

FIG. 4 is an enlarged cross-sectional view of the seal assembly of theembodiment shown in FIGS. 1 and 2 showing fluid flow into the combustionchamber.

FIG. 5 is a top view of the seal used with one embodiment of the presentinvention.

FIG. 6 is an enlarged cross-sectional view of the seal shown in FIG. 5.

FIG. 7 is a cross-sectional view of one embodiment of the presentinvention of a hybrid case-burning rocket booster.

FIG. 8 is an enlarged cross-sectional view of the assembly of theembodiment shown in FIG. 7 showing fluid and oxidizer flow into thecombustion chamber.

FIG. 9 is a perspective view of one embodiment of the composite steelrod of the present invention.

FIG. 10 is a partial cross-sectional view of composite steel rod of thepresent invention showing a mandrel being pulled through a collapsedsleeve disposed in the rod.

FIG. 11 is a view of the rod shown in FIG. 10 taken along the 11—11section line.

FIG. 12 is a view of the rod shown in FIG. 11 taken along the 12—12section line.

FIG. 13 is an enlarged drawing of one embodiment of the drive system ofthe present invention.

FIG. 14 is a view of the drive system shown in FIG. 13 taken along theC—C section line.

FIG. 15 is a schematic view of sealing system of the embodiment shown inFIGS. 1 and 2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 1, one embodiment of the present invention of acase-burning rocket booster 10 includes a case 12 containing a solidrocket fuel 14 (see FIGS. 3 and 4), a combustion chamber 16 connected tothe case 12 for burning the case 12 and the fuel 14, a nozzle 18connected to the combustion chamber 16 for expelling the burned case andfuel to generate thrust, and a drive system 20 connected to thecombustion chamber 16 for pulling the combustion chamber 16 and nozzle18 up the case 12 as the case 12 and the fuel 14 burn.

The case 12 is made out of a structural but combustible material and isburned in the combustion chamber 16 along with the solid rocket fuel 14.As the case burns, the overall thrust provided by the booster 10increases because of the additional mass flow through the nozzle 18. Inone embodiment, the case is made out of a graphite epoxy composite andincludes a combustion enhanced epoxy resin. This type of structuralmaterial is best suited for large-scale rocket motors because of itshigh strength to weight ratio, its smooth outer surface and its ease offabrication. In other embodiments, however, the case can be made out ofother combustible materials. In this embodiment, the case 12 includes alayer of oxidizer rich fuel next to the case wall (not shown) to enhancethe burning of the case 12 in the combustion chamber 16.

One advantage provided by the case-burning rocket booster 10 of thepresent invention is the fact that the case 12 is burned and thenexpelled through the nozzle 18 to produce a net gain in thrust. Anotheradvantage is the fact that the booster 10 of the present invention doesnot require a layer of insulation inside the case 12 to protect the casefrom exposure to the heat of combustion.

The case 12 is designed to be combustible at a temperature generated inthe combustion chamber, which is approximately 6,000 degrees Fahrenheit.In most applications, this temperature will provide sufficient heat toassure combustion of a graphite epoxy composite case. In applicationswhere this temperature is insufficient to assure combustion, anothermaterial must be added to the composite case 12 to assure combustion ofthe case 12. Finally, if necessary, combustible metallic powder, such asaluminum or magnesium powder, may be added to the epoxy resin, orcombustible metallic threads, such as aluminum or magnesium threads, maybe added to the graphite weave to enhance the combustion rate of thecase 12.

The case 12 is also designed to withstand the pressures generated by aconventional combustion chamber. While combustion pressures can varydepending on the application and the rocket size, most larger rocketboosters will have chamber pressures of approximately 500 pounds persquare inch. Accordingly, in this embodiment, the case 12 has a casewall thickness of approximately 1.5 inches. In other applications, wherethe combustion chamber pressures are greater, the case 12 may require awall thickness greater than 1.5 inches.

Referring to FIGS. 13 and 14, the drive system 20 includes a series ofmetal threaded rods 22 and a motor or engine 75, which is enclosed in abase 26. The motor or engine 75 is connected to the threaded rods 22 andis operable to turn the threaded rods 22 as the case 12 and fuel 14 areburned in the combustion chamber 16, thereby pulling the combustionchamber 16 and nozzle 18 up the case 12. In the embodiment shown inFIGS. 13 and 14, the turbine engine 75 burns tanked liquid fuel andoxidizer 77, which is supplied to the engine 75 through an inlet 79,located in the base 26. Engine exhaust is directed away from the system20 through an exhaust port 80. The amount of fuel 77 supplied to theengine 75 is determined by the required speed for the threaded rods 22.The required speed of the threaded rods is, in turn, determined by therate at which the case 12 and fuel 14 burn. The case and fuel burn rateis determined by either a direct feed back system (not shown), such asthermal couples (not shown), that measures the rate of solid fuel andcase combustion or a pre-programmed drive rate that matches thepredicted burn rates of the solid fuel 14 and case 12.

The turbine engine 75 drives a high reduction gear train 78 in aself-contained housing. The gear train 78 includes an output shaft 70and an output gear 71 that is supported by a bearing 74. The output gear71 meshes with the main rod drive gears 72 located on each of thethreaded rods 22. The drive gears 72 are held in place by nuts 73attached to the threaded rod 22 and supported by a thrust bearing 76. Inthis embodiment, a ring gear 81 mechanically equalizes the position ofall the gears 72 in the drive system 20.

In an alternative embodiment, the metal threaded rods 22 are replacedwith a composite/steel threaded tension rod 21 (See FIG. 9). The rod 21is fabricated by pulling epoxy resin saturated graphite yarn 61 wrappedaround a metal collapsed sleeve 63 through a hardened steel outer tube62. A mandrel 64 is then pulled through the collapsed sleeve 63 using apull rod or cable 67, thereby expanding the sleeve 63 and compressingthe mix of graphite yarn 61 and epoxy resin 65 against the outer tube62. As a result, excess epoxy resin 65 and air bubbles 66 are forced outof the tube 62. This method of fabrication provides the same compressioneffect as an auto-clave. A conventional auto-clave, however, can only beused to provide external pressure. The graphite/epoxy mix, the expansionsleeve, and the outer threaded shell are bonded together as the resincures to form a lightweight completed assembly

The combustion chamber 16 is cylindrical in shape and includes a seriesof flanges 28 having threaded openings 29 so that the combustion chamber16 is pulled up the case 12 toward the base 26 when the motor or enginerotates the threaded rods 22. In one embodiment, the combustion chamber16 also includes a layer of insulation 23 (see FIG. 3) for protectingthe interior of cavity 24 of combustion chamber 16 from the heat ofcombustion. In an alternative embodiment, the threaded rods 22 aredesigned to be broken apart using explosive cutting charges (not shown)as the rods 22 pass through the threaded openings 29, thereby reducingthe weight of the booster 10 and preventing portions of the threadedrods 22 from extending into the rocket exhaust as the fuel 14 burns. Inanother alternative embodiment, the drive system 20 includes cables andspools instead of threaded rods to move the combustion chamber 16 andnozzle 18 up the case 12.

Referring to FIGS. 2 and 3, the combustion chamber 16 is sealed to thecase 12 using a unique sealing systems 29 (see FIG. 15), which preventshigh temperature gasses from escaping from the combustion chamber 16.The system 29 includes a pair of seals, 30 and 32, with fluid trappedbetween the two seals in a fluid compartment 48, to prevent combustionleaks. In one embodiment, seal 30 includes two heat-resistant metalrings, 34 and 36, and seal 32 includes an elastomer ring 38 to preventfluid from passing by seal 38 and a backing ring 40 (see FIGS. 4–6). Therings, 34 and 36, include a series of notches 35, which allow some fluidto flow past the rings. When in use, the rings, 34 and 36, are orientedso that the notches 35 of each ring are misaligned. As a result, whilethe rings, 34 and 36, prevent a substantial portion of any fluid frompassing the rings, some fluid can pass through the notches 35 of onering and then through the notches 35 of the other ring into thecombustion chamber 16.

Referring to FIG. 15, the sealing system 29 also includes a fluid supplysystem 43 that includes a fluid container 44, a fluid channel 46, and apump 45, and a fluid pressure control system 47, which includes apressure control valve 49, a pressure modulator 51, and a pressuretransducer 53 to measure combustion chamber pressure.

To prevent super hot rocket gasses from blowing past the seals, fluid 42is pumped, using the pump 45, from the fluid container 44 (FIG. 2) intothe combustion chamber 16 through the fluid channel 46 and into fluidcompartment 48 located between seal 30 and seal 32. The pressure of thefluid 42 between the seals (hereinafter referred to as the “sealpressure”) is maintained above the pressure in the combustion chamber 16using the fluid pressure control system 47.

At rocket booster start up, the pump 45 pressurizes the fluidcompartment 48 to a seal pressure that is a preset differential pressureabove the anticipated start up combustion chamber pressure. In oneembodiment, a start up algorithm contained in the pressure modulator 51selects a preset differential pressure of approximately 50 pounds persquare inch (PSI) and maintains seal pressure approximately 50 PSI abovethe anticipated start up combustion chamber pressure. As soon as theseal pressure reaches the preset differential pressure above thecombustion chamber pressure, the pressure modulator 51 provides a datasignal to a rocket control circuitry (not shown) to ignite the rocketfuel 14. Once the fuel 14 is ignited, the pressure transducer 53provides a combustion chamber pressure data signal to the fluid pressurecontrol system 51. Based on the combustion chamber pressure data signal,the pressure modulators 51 directs the pressure control valve 49 toincidentally open or close in order to maintain seal pressure between 20to 70 PSI above the combustion chamber 16 pressure through out therocket burn cycle. The pressure modulator 51 contains an algorithm thatassures that sufficient fluid 42 flows through the fluid compartment 48to prevent over heating of the seals 19, 20, 38 and 40. The pressurecontrol valve 49 provides fluid pressure data back to the pressuremodulator 51 during all operations.

As a result of the pressure differential between the seal pressure andthe combustion chamber pressure, some fluid 42 leaks past seal 30 and isburned in the combustion chamber 16. This leakage prevents overheatingof the fluid 42 between the seals, 30 and 32. Furthermore, as theleakage fluid vaporizes in the combustion chamber 16, it absorbs heatand prevents the seal 30 and case 12 from being exposed to excessiveheat in the low temperature volume area 15 (see FIG. 15) in thecombustion chamber. The combustion chamber insulation liner 23 isprofiled in a manner that causes this low temperature volume area to becreated. In one alternative embodiment, the fluid 42 is flammable tofacilitate case combustion and provides initial burning and heating ofthe case 12.

Referring to FIGS. 7 and 8, one embodiment of the present invention of ahybrid case-burning rocket booster 50 is shown. The hybrid booster 50 isidentical to the booster 10 discussed above with the exception of anoxidizer supply system 52. In addition, in some alternative embodiments,the drive system 20 and the combustion chamber 16 can be reduced insize. This hybrid concept provides the ability to throttle the rocketduring ascent as well as provides a way to terminate combustion, andrestart combustion if necessary. More specifically, the hybrid booster50 includes the case 12, combustion chamber 16, nozzle 18, and drivesystem 20 of the booster 10 described in detail above. The oxidizersupply system 52 includes a liquid oxidizer tank 54 and an oxidizerchannel 56 for supplying liquid oxidizer 58 to the combustion chamber16, which increases the amount of thrust generated by the booster 50when compared to the thrust generated by burning only the case 12 andfuel 14. In addition, the oxidizer supply system 52 also includes athrottle assembly (not shown) for controlling the amount of liquidoxidizer 58 supplied to the combustion chamber 16 and therebycontrolling the amount of thrust generated by the booster 50. Using theoxidizer supply system 52, the hybrid booster 50 can be throttled in amanner that is similar to a liquid rocket without the need for cryogenicstorage of hydrogen.

Thus, although there have been described particular embodiments of thepresent invention of a new and useful Case Burning Rocket, it is notintended that such references be construed as limitations upon the scopeof this invention except as set forth in the following claims.

1. A rocket booster, comprising: a combustible case containing solid rocket fuel; a combustion chamber assembly adjustably coupled to the case; a sealing system connected to the combustion chamber assembly, the sealing system including a pair of grooves defined in a portion of the combustion chamber assembly adjacent to the case, a fluid compartment defined in the portion of the combustion chamber assembly adjacent to the case and positioned between the pair of grooves, seals disposed in the pair of grooves and positioned adjacent to the case, a fluid supply system connected to the fluid compartment, and a fluid pressure control system connected to the fluid supply system; a nozzle connected to the combustion chamber assembly; and a drive system coupled to the combustion chamber assembly and the case.
 2. The booster of claim 1, wherein the fluid supply system includes a fluid container, a fluid channel connecting the fluid container to the fluid compartment, and a pump connected to the fluid channel.
 3. The booster of claim 2, wherein the fluid pressure control system includes a pressure control valve connected to the fluid channel, a pressure modulator connected to the pressure control valve, and a pressure transducer connected to the pressure modulator.
 4. The booster of claim 1, wherein the pair of grooves includes: a lower seal groove defined in the portion of the combustion chamber adjacent to the case and positioned between the fluid compartment and an interior cavity of the combustion chamber; and an upper seal groove defined in the portion of the combustion chamber adjacent to the case and positioned above the lower seal groove.
 5. The booster of claim 1, wherein: the seals in the lower seal groove including a pair of rings having one or more notches and oriented so that the notches on each of the rings are misaligned; and the seals in the upper groove include an elastomer ring and a backing ring.
 6. The booster of claim 1, wherein the combustible case includes a graphite epoxy resin composite material, a combustion enhanced epoxy resin, a layer of oxidizer rich fuel, powdered combustible metal, combustible metal threads, or any combination thereof.
 7. The booster of claim 1, wherein the drive system including a plurality of threaded rods rotatably connected to the combustion chamber assembly and a motor or engine coupled to the plurality of threaded rods.
 8. The booster of claim 7, wherein each of the plurality of threaded rods includes a steel threaded outer layer and a graphite epoxy composite core.
 9. The booster of claim 1, further comprising an oxidizer supply system connected to the combustion chamber.
 10. A rocket booster, comprising: a combustible case containing solid rocket fuel, the combustible case including a graphite epoxy resin composite material, a combustion enhanced epoxy resin, a layer of oxidizer rich fuel, magnesium powder, magnesium threads, or any combination thereof, a combustion chamber assembly adjustably coupled to the case and having an associated combustion chamber pressure, the combustion chamber assembly including: a fluid compartment defined in a portion of the combustion chamber assembly adjacent to the case and containing a fluid, the fluid having a fluid pressure that is greater than the combustion chamber pressure; a lower seal groove defined in the portion of the combustion chamber assembly adjacent to the case and positioned between the fluid compartment and an interior cavity of the combustion chamber assembly; an upper seal groove defined in the portion of the combustion chamber assembly adjacent to the case and positioned above the lower seal groove; and seals inserted into the upper and lower seal grooves and positioned adjacent to the case; a nozzle connected to the combustion chamber assembly; and a drive system coupled to the combustion chamber assembly and the case.
 11. A rocket booster, comprising: a combustible case containing solid rocket fuel; a combustion chamber assembly adjustably coupled to the case; sealing means for coupling the combustion chamber assembly to the combustible case, the sealing means including sufficient fluid to prevent gases from passing between the combustion chamber assembly and the combustible case; a nozzle connected to the combustion chamber assembly; and a drive system coupled to the combustion chamber assembly and the case.
 12. The rocket booster of claim 11, wherein the sealing means includes a fluid supply means for supplying the fluid used to prevent gasses from passing between the combustion chamber assembly and the combustible case.
 13. The rocket booster of claim 11, wherein the sealing means includes a fluid pressure control means for causing the fluid in the sealing means to have a fluid pressure that prevents gasses from passing between the combustion chamber assembly and the combustible case.
 14. The booster of claim 11, wherein the sealing means includes a pair of grooves defined in a portion of the combustion chamber assembly adjacent to the combustible case and a fluid compartment defined in the portion of the combustion chamber assembly adjacent to the case and positioned between the pair of grooves.
 15. The booster of claim 14, wherein the sealing means includes seals disposed in the pair of grooves and positioned adjacent to the case.
 16. The booster of claim 15, wherein the sealing means includes a fluid supply system connected to the fluid compartment.
 17. The booster of claim 16, wherein the sealing means includes a fluid pressure control system connected to the fluid supply system.
 18. A method of generating thrust using a solid rocket booster, the booster including a combustible case containing solid rocket fuel, a combustion chamber adjustably coupled to the case using a sealing system, and a nozzle connected to the combustion chamber, comprising the steps of: burning the case and fuel in the combustion chamber and expelling the burned case and fuel out through the nozzle to generate thrust; moving the combustion chamber and nozzle up the case as the case and fuel burn; and injecting fluid into a portion of the sealing system to prevent combustion leaks while burning the case and fuel.
 19. The method of claim 18, further comprising the step of controlling the injection of fluid so that the fluid has a fluid pressure that is greater than a combustion chamber pressure associated with the combustion chamber. 